Multiple timing advance and carrier aggregation

ABSTRACT

At least one of transmissions and receptions over allocated radio resources within a first timing advance group are synchronized using a first timer; and similar for allocated radio resources within a second timing advance group that are synchronized using a second timer. In response to determining that the first timer remains synchronized while the second timer is not synchronized with a radio network which has allocated the respective radio resources, a first procedure is followed for the case in which there is a primary component carrier within the second timing advance group and a different second procedure for the case in which there is no primary component carrier within the second timing advance group. In an exemplary embodiment, a message is sent to the radio network indicating that the second timer has expired. Various distinctions between the two procedures, and how the message is sent, are detailed for different embodiments.

TECHNICAL FIELD

The exemplary and non-limiting embodiments of this invention relategenerally to wireless communication systems, methods, devices andcomputer programs and, more specifically, relate tosynchronization/timing alignment timers in a communication system whichemploys carrier aggregation.

BACKGROUND

This section is intended to provide a background or context to theinvention that is recited in the claims. The description herein mayinclude concepts that could be pursued, but are not necessarily onesthat have been previously conceived or pursued. Therefore, unlessotherwise indicated herein, what is described in this section is notprior art to the description and claims in this application and is notadmitted to be prior art by inclusion in this section.

The following abbreviations that may be found in the specificationand/or the drawing figures are defined as follows:

3GPP third generation partnership project

ARQ automatic repeat request

BSR buffer status report

CA carrier aggregation

CC component carrier

CE control element

DL downlink (eNB to UE)

eNB EUTRAN Node B (evolved Node B/base station)

E-UTRAN evolved UTRAN (LTE)

HARQ hybrid ARQ

LTE long term evolution

MAC medium access control

NACK negative acknowledgment

PCC primary component carrier

PDCCH physical downlink control channel

PUCCH physical uplink control channel

RACH random access channel

RRC radio resource control

SCC secondary component carrier

SR scheduling request

SRS sounding reference signal

UE user equipment

UL uplink (UE to eNB)

UTRAN universal terrestrial radio access network

In the communication system known as evolved UTRAN (E-UTRAN, alsoreferred to as UTRAN-LTE or E-UTRA), the LTE Release 8 is completed, theLTE Release 9 is being standardized, and the LTE Release 10 is currentlyunder development within the 3GPP. In LTE the downlink access techniqueis orthogonal frequency multiple division access OFDMA, and the uplinkaccess technique is single carrier, frequency division multiple accessSC-FDMA. These access techniques are expected to continue in LTE Release10.

FIG. 1 reproduces FIG. 4.1 of 3GPP TS 36.300, V8.6.0 (2008-09), andshows the overall architecture of the E-UTRAN system. The EUTRAN systemincludes eNBs, providing the EUTRA user plane and control plane (RRC)protocol terminations towards the UE. The eNBs are interconnected witheach other by means of an X2 interface. The eNBs are also connected bymeans of an S1 interface to an evolved packet core, more specifically toa MME and to a Serving Gateway. The S1 interface supports a many to manyrelationship between MMEs/Serving Gateways and the eNBs.

Of particular interest herein are the further releases of 3GPP LTEtargeted towards future international mobile telecommunications(IMT)-advanced systems, referred to herein for convenience simply asLTE-Advanced (LTE-A). LTE-A is directed toward extending and optimizingthe 3GPP LTE Release 8 radio access technologies to provide higher datarates at very low cost. LTE-A will most likely be part of LTE Release 10which is to be backward compatible with LTE Release 8 and to includebandwidth extensions beyond 20 MHz, among others. For an overview seefor example 3GPP TR 36.913 v9.0.0 (2009-12) Requirements for furtheradvancements for Evolved Universal Terrestrial Radio Access (E-UTRA)(LTE Advanced) (Release 9).

The bandwidth extension in LTE Release 10 is to be done via carrieraggregation (CA), in which several Release 8 compatible carriers areaggregated together to form a system bandwidth. This is shown by exampleat FIG. 2 in which there are five Release 8 compatible CCs aggregated toform one larger LTE Release 10 bandwidth. Existing Release 8 terminalscan receive and/or transmit on one of the CCs for backwardcompatibility, while future LTE-A terminals could potentiallyreceive/transmit on multiple CCs at the same time to give the eNBgreater scheduling flexibility while increasing data throughput.

In cellular radio systems generally, the user equipments adjust thetiming of their transmissions to the base station so that the times wheneach transmitted symbol arrives at the eNB's receiver are within at mosta small timing offset of the times when the eNB is expecting them. Thisexample is uplink time alignment.

Specifically for the LTE Release 8/9 system, the UE synchronizes itsuplink transmissions by first synchronizing with the eNB's transmissionsin the downlink (by detecting bit and frame timing), and thentransmitting at a fixed delay (stipulated by a the controlling radiostandard) relative to the downlink, the delay further reduced by atiming advance. The timing advance compensates for the round trippropagation delay between the eNB and the UE and varies with time, dueto the UEs mobility.

The UE operating in an LTE Release 8/9 system obtains the correct timingduring its initial entry into the network, which is done via a RACHprocedure that does not require pre-existing timing synchronizationbetween the accessing UE and the network. Once established in thenetwork the UE's timing is kept in alignment by a MAC CE, which the eNBtransmits to a specific UE when it detects that the UE's uplinktransmission timing is in error.

The UE tracks its timing alignment by means of a time alignment timer,which is started or restarted whenever a timing correction is received(either in a MAC CE or a Random Access Response). If the timingalignment expires, the UE is required to act as if timing alignment hasbeen lost. For the LTE Release 8 cellular radio system, a UE whosetiming alignment timer has expired is required [by 3GPP TS36.321 section5.2] to:

-   -   flush all HARQ buffers;    -   notify RRC to release PUCCH/SRS; and    -   clear any configured downlink assignments and uplink grants.

In LTE Release 8 the UE does not initiate RACH transmissions to keep inuplink time alignment, these must be triggered by the eNB. The eNB cankeep a non-transmitting UE in uplink time alignment by instructing it,via a PDCCH order that is transmitted on the PDCCH to transmit on theRACH.

Flushing the HARQ buffers deletes all information pendingtransmission/re-transmission from the HARQ level. Releasing thePUCCH/SRS removes the uplink control channel that the UE uses totransmit ACK/NACK reports, CQI measurement reports and SR bits that areused to indicate that the UE has uplink data to send. Clearing theconfigured downlink assignments and uplink grants removes all current orpending opportunities/requirements for uplink transmission.

Once a UE loses its uplink time alignment in an LTE Release 8 system itis not permitted to transmit in the uplink, except on the RACH. In thecurrent 3GPP LTE specification, expiry of the time alignment timeritself does not trigger the UE to initiate a RACH transmission.

The UE with lost timing synchronization continues to receive the PDCCHcontrol channel in LTE Release 8, but does not transmit in the uplink,unless one of the following occurs:

-   -   It receives on its downlink control channel a PDCCH order        command that triggers it to transmit on RACH and receive a time        alignment correction in response. This will bring the UE into        uplink time alignment and enable it to transmit in the uplink.        The Time Alignment Timer is restarted.    -   It has new uplink data to transmit which triggers the sending of        buffer status report (BSR). This will, in turn, trigger the UE        to transmit on RACH in order receive a grant to send the BSR.        The Random Access Response will also provide the timing        correction that will bring the UE into uplink time alignment.

But in LTE Release 8/9 there is no CA, and so each UE tracks its timingsynchronization with the eNB by a single timing alignment timer. In theCA arrangement of spectrum as in LTE Release 10, a single UE may beassigned radio resources on more than one CC. In some cases more thanone CC is aligned in time and so the same timing alignment timer can beused for them all. Such timing-dependent CCs for which the UE trackstiming synchronization by a single timing alignment timer are termed atiming advance group of CCs, and there may be only one or more than oneCC in any timing advance group. In other cases at least two of the CCsassigned to the LTE Release 10 UE are timing independent, and so the UEmust maintain a separate timing advance timer for each of the differenttiming advance groups it is assigned. Currently it is not specified howa UE should respond in the case where one but not all timing alignmenttimer expires for a UE that is operating with two or more timing advancegroups.

To extend the LTE Release 8/9 rules for the case of lost timingsynchronization on less than all configured timing advance groups wouldbe to dis-allow the UE from transmitting in the uplink on any of itsconfigured CCs. This result would waste the capacity of the uplinkcarriers for which the UE still has timing alignment. Alternatively, theeNB can keep the UE in timing alignment for all its configured carriersby way of a MAC CE and/or PDCCH order procedures. However, errors inacknowledgement (NACK to ACK errors in which a UE's NACK sent withimproper timing is interpreted by the eNB as an ACK) at the HARQ levelfor such MAC CE corrections can mean that the eNB thinks that the UE istime aligned whereas one or more of that same UE's time alignment timershave expired. In principle, the eNB could also allow timing alignment totemporarily lapse for one or more of the UE's configured timing groups,but not the timing group which includes the UE's primary CC. But in thiscase the UE will not know whether or not the expired timing alignmenttimer was intended by the network.

SUMMARY

In accordance with a first aspect the exemplary embodiments of theinvention include a method comprising: an apparatus synchronizing atleast one of transmissions and receptions over allocated radio resourceswithin a first timing advance group using a first timer; the apparatussynchronizing at least one of transmissions and receptions overallocated radio resources within a second timing advance group using asecond timer; and in response to determining that the first timerremains synchronized while the second timer is not synchronized with aradio network which has allocated the respective radio resources, theapparatus following a first procedure for the case in which there is aprimary component carrier within the second timing advance group andfollowing a different second procedure for the case in which there is noprimary component carrier within the second timing advance group.

In accordance with a second aspect the exemplary embodiments of theinvention include a memory storing a program of computer readableinstructions that when executed by a processor result in actionscomprising: synchronizing at least one of transmissions and receptionsover allocated radio resources within a first timing advance group usinga first timer; synchronizing at least one of transmissions andreceptions over allocated radio resources within a second timing advancegroup using a second timer; and in response to determining that thefirst timer remains synchronized while the second timer is notsynchronized with a radio network which has allocated the respectiveradio resources, following a first procedure for the case in which thereis a primary component carrier within the second timing advance groupand following a different second procedure for the case in which thereis no primary component carrier within the second timing advance group.

In accordance with a third aspect the exemplary embodiments of theinvention include an apparatus comprising at least one processor and atleast one memory including computer program code. In this third aspectthe at least one memory and the computer program code are configured,with the at least one processor, to cause the apparatus to at least:synchronize at least one of transmissions and receptions over allocatedradio resources within a first timing advance group using a first timer;synchronize at least one of transmissions and receptions over allocatedradio resources within a second timing advance group using a secondtimer; and in response to determining that the first timer remainssynchronized while the second timer is not synchronized with a radionetwork which has allocated the respective radio resources, follow afirst procedure for the case in which there is a primary componentcarrier within the second timing advance group and follow a differentsecond procedure for the case in which there is no primary componentcarrier within the second timing advance group.

These and other aspects are set forth in further detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 reproduces FIG. 4 of 3GPP TS 36.300 (v8.6.0), and shows theoverall architecture of the E-UTRAN system.

FIG. 2 is a schematic diagram of a radio spectrum in whichcross-scheduling can be employed, in which five component carrierbandwidths are aggregated into a single LTE Release 10 bandwidth.

FIG. 3 shows a simplified block diagram of certain apparatus accordingto various exemplary embodiments of the invention.

FIG. 4 shows a more particularized block diagram of a user equipmentsuch as that shown at FIG. 4.

FIG. 5 is a logic flow diagram that illustrates the operation of amethod, and a result of execution of computer program instructionsembodied on a computer readable memory, in accordance with the exemplaryembodiments of this invention.

DETAILED DESCRIPTION

The examples below are in the context of a LTE Release 10 system but maybe employed with any CA type wireless communication system. FIG. 2 isspecific to LTE Release 10 but still shows the general concept of CA;smaller frequency chunks such as for example 1.4 MHz, 5 MHz and 10 MHzCCs can be aggregated, and the total CA bandwidth can be less than orgreater than 100 MHz. Some CA systems or embodiments may havenon-contiguous CCs (for example the spectrum blocks forming the CCsmight be far apart in terms of frequency such as 700 MHz and 2.1 GHz).Other CA systems or embodiments may have an asymmetric DL/UL CA whichfor example may be built into a CA system by combining a frequencydivision duplex FDD component carrier with a time division duplex TDDcomponent carrier. LTE Release 10 is not the only CA-type system but isused in the examples here to explain the invention using specificexamples, and so the concepts detailed below are not limited only to theLTE Release 10 system.

Refer to FIG. 3 for a simplified block diagram of various electronicdevices and apparatus that are suitable for use in practicing theexemplary embodiments of this invention. In FIG. 3 a wireless network 1is adapted for communication over a wireless link 11 with an apparatus,such as a mobile communication device which above is referred to as a UE10, via a network access node, such as a Node B (base station), and morespecifically an eNB 12. The network 1 may include a network controlelement (NCE) 14 that may include the mobility entity/serving gatewayMME/S-GW functionality shown in FIG. 1A, and which provides connectivitywith a network, such as a telephone network and/or a data communicationsnetwork (e.g., the internet). The UE 10 includes a controller, such as acomputer or a data processor (DP) 10A, a computer-readable memory mediumembodied as a memory (MEM) 10B that stores a program of computerinstructions (PROG) 10C, and a suitable radio frequency (RF) transceiver10D for bidirectional wireless communications with the eNB 12 via one ormore antennas. The eNB 12 also includes a controller, such as a computeror a data processor (DP) 12A, a computer-readable memory medium embodiedas a memory (MEM) 12B that stores a program of computer instructions(PROG) 12C, and a suitable RF transceiver 12D for communication with theUE 10 via one or more antennas. The eNB 12 is coupled via a data/controlpath 13 to the NCE 14. The path 13 may be implemented as the S1interface shown in FIG. 1A. The eNB 12 may also be coupled to anothereNB via data/control path 15, which may be implemented as the X2interface shown in FIG. 1A.

At least one of the PROGs 10C and 12C is assumed to include programinstructions that, when executed by the associated DP, enable the deviceto operate in accordance with the exemplary embodiments of thisinvention, as will be discussed below in greater detail.

That is, the exemplary embodiments of this invention may be implementedat least in part by computer software executable by the DP 10A of the UE10 and/or by the DP 12A of the eNB 12, or by hardware, or by acombination of software and hardware (and firmware).

For the purposes of describing the exemplary embodiments of thisinvention the UE 10 may be assumed to also include a plurality of timingadvance group timers 10E, and the eNB 12 may include a plurality oftiming advance group timers 12E. Shown at FIG. 3 are N such timers ineach of the UE 10 and the eNB 12, in which N is an integer equal to thenumber of CCs in the CA system (and the N timers shown for the eNB arereserved per UE). A number of these timers may run independently,according to the number of timing independent groups of CCs that areassigned to the UE in a given cell. By example the timers may beoscillators (voltage controlled or numerically controlled) within anyone of the various processors shown at FIGS. 3-4, or they may bestand-alone timers/oscillators/counters such as are shown at FIG. 3 astimers 10E and 12E. Also at FIG. 3 is a PCC tracker 10F which tracks forthe UE 10 in which timing advance group its primary component carrierPCC lies. When one of the N timers expires, this tracker 10F compareswhether the group having the expired timer does or does not carry theUE's assigned PCC. Different procedures are followed if the timingadvance group associated with the expired timer includes or not the PCC,as is detailed further below by example. In an exemplary embodiment thefunction of the PCC tracker 10F is incorporated into the main processor10A or any of the other processors/chips shown at FIG. 4.

In general, the various embodiments of the UE 10 can include, but arenot limited to, cellular telephones, personal digital assistants (PDAs)having wireless communication capabilities, portable computers havingwireless communication capabilities, image capture devices such asdigital cameras having wireless communication capabilities, gamingdevices having wireless communication capabilities, music storage andplayback appliances having wireless communication capabilities, Internetappliances permitting wireless Internet access and browsing, as well asportable units or terminals that incorporate combinations of suchfunctions.

The computer readable MEMs 10B and 12B may be of any type suitable tothe local technical environment and may be implemented using anysuitable data storage technology, such as semiconductor based memorydevices, flash memory, magnetic memory devices and systems, opticalmemory devices and systems, fixed memory and removable memory. The DPs10A and 12A may be of any type suitable to the local technicalenvironment, and may include one or more of general purpose computers,special purpose computers, microprocessors, digital signal processors(DSPs) and processors based on a multicore processor architecture, asnon-limiting examples.

FIG. 4 illustrates further detail of an exemplary UE in both plan view(left) and sectional view (right), and the invention may be embodied inone or some combination of those more function-specific components. AtFIG. 4 the UE 10 has a graphical display interface 20 and a userinterface 22 illustrated as a keypad but understood as also encompassingtouch-screen technology at the graphical display interface 20 andvoice-recognition technology received at the microphone 24. A poweractuator 26 controls the device being turned on and off by the user. Theexemplary UE 10 may have a camera 28 which is shown as being forwardfacing (e.g., for video calls) but may alternatively or additionally berearward facing (e.g., for capturing images and video for localstorage). The camera 28 is controlled by a shutter actuator 30 andoptionally by a zoom actuator 32 which may alternatively function as avolume adjustment for the speaker(s) 34 when the camera 28 is not in anactive mode.

Within the sectional view of FIG. 4 are seen multiple transmit/receiveantennas 36 that are typically used for cellular communication. Theantennas 36 may be multi-band for use with other radios in the UE. Thepower chip 38 controls power amplification on the channels beingtransmitted and/or across the antennas that transmit simultaneouslywhere spatial diversity is used, and amplifies the received signals. Thepower chip 38 outputs the amplified received signal to theradio-frequency (RF) chip 40 which demodulates and downconverts thesignal for baseband processing. The baseband (BB) chip 42 detects thesignal which is then converted to a bit-stream and finally decoded.Similar processing occurs in reverse for signals generated in theapparatus 10 and transmitted from it.

Signals to and from the camera 28 pass through an image/video processor44 which encodes and decodes the various image frames. A separate audioprocessor 46 may also be present controlling signals to and from thespeakers 34 and the microphone 24. The graphical display interface 20 isrefreshed from a frame memory 48 as controlled by a user interface chip50 which may process signals to and from the display interface 20 and/oradditionally process user inputs from the keypad 22 and elsewhere.

Certain embodiments of the UE 10 may also include one or more secondaryradios such as a wireless local area network radio WLAN 37 and aBluetooth® radio 39, which may incorporate an antenna on-chip or becoupled to an off-chip antenna. Throughout the apparatus are variousmemories such as random access memory RAM 43, read only memory ROM 45,and in some embodiments removable memory such as the illustrated memorycard 47 on which the various programs 10C are stored. All of thesecomponents within the UE 10 are normally powered by a portable powersupply such as a battery 49.

The aforesaid processors 38, 40, 42, 44, 46, 50, if embodied as separateentities in a UE 10 or eNB 12, may operate in a slave relationship tothe main processor 10A, 12A, which may then be in a master relationshipto them. Embodiments of this invention need not be disposed in anyindividual processor/chip but may be disposed across various chips andmemories as shown or disposed within another processor that combinessome of the functions described above for FIG. 4. Any or all of thesevarious processors of FIG. 4 access one or more of the various memories,which may be on-chip with the processor or separate therefrom. Similarfunction-specific components that are directed toward communicationsover a network broader than a piconet (e.g., components 36, 38, 40,42-45 and 47) may also be disposed in exemplary embodiments of theaccess node 12, which may have an array of tower-mounted antennas ratherthan the two shown at FIG. 5B.

Note that the various chips (e.g., 38, 40, 42, etc.) that were describedabove may be combined into a fewer number than described and, in a mostcompact case, may all be embodied physically within a single chip.

The background section above details that it is not yet known how tohandle the case in which a UE, having more than one timing advancegroups of CCs (each group having one or more CCs), finds that it haslost synchronization with the access node/eNB for one of the groups butnot for all of them. In LTE Release 10 this timing synchronization iskept by a group-specific timing advance timer and synchronization islost for a timing advance group when the timing advance timer for thatgroup expires.

The exemplary embodiments detailed below concern the case in which theUE is assigned more than one timing advance group, in which each timingadvance group uses a timing correction that is different from othergroup's corrections. Specific but non-limiting examples of this includea CC for UL and another CC for DL in one group and one CC for both ULand DL in another group, or only a single CC for UL and DL in each of afirst and second timing advance group, or two or more CCs for UL and DLin one group and one or more CCs for UL and DL in another CC and one ormore CCs for UL and DL in a third group. The examples below describe theexemplary embodiments in the context of two timing advance groups whichare timing-independent and so are tracked by the UE 10 and eNB 12 eachusing two timers, but the UE may have a third or more groups that aretiming independent of the first and second timing advance groups. Anytiming advance group can have one or more CCs. All CCs in a timingadvance group use the same timer for synchronization between the UE andthe eNB.

By example, the need for different timing corrections may arise due tothe carrier aggregation being performed in different bands e.g. 700 MHzand 2.0 GHz and transmissions for one of the bands are routed via arepeater or relay node and for the other band they are not. In anotherexample it may arise if transmissions for one of the bands are routedthrough a different antennae system to those of the other band and theantenna systems are located some distance apart (remote radio heads).The effect is that the path lengths between the eNB and the UE aredifferent for the two bands and the path lengths can vary independentlywith changes in UE position. These are non-limiting examples only.

The LTE Release 10 UE 10 which supports independent timing alignment fortwo or more groups of uplink carriers will need to maintain the timealignment for each of the timing alignment groups in response to timingcorrections received from the eNB 12, and it will need to detect when ithas lost time alignment for the group and take the action needed toprevent itself from transmitting in the uplink when the UE 10 has losttiming alignment. The UE 10 will maintain a time alignment timer 10E foreach group (one or more) of uplink component carriers assigned to the UE10 that share a common timing advance, restarting the timer 10E when atiming correction for the group of channels is received in a MAC CE orRACH response. When a PDCCH order is received, the UE 10 also initiatesthe appropriate RACH procedure. And when a timing correction is receivedeither in a MAC CE or a Random Access Response, the UE 10 identifies thegroup of uplink carriers (component carriers) to which it applies (whichis the timing advance group) and pass the timing correction from the MAClayer to the physical layer for each of the carriers in the group.

For the case in which the time alignment timer 10E expires for aparticular group, the UE implements the actions to be completed whentiming alignment is lost for that group of uplink carriers. As notedabove in the background section, in LTE Release 8 those actions were toclear all HARQ buffers, notify RRC to release PUCCH/SRS; and clear anyconfigured downlink assignments and uplink grants. But LTE Release 8does not use CA and so there is no case in which the UE can have itstimer expire for one timing advance group but not another.

In the development of LTE Release 10, the configured set of CCs for a UEis always to consist of one DL primary CC (PCC), one UL PCC, and zero,one or more secondary CCs (SCCs) [further details in this regard may beseen at document R2-101846 entitled “Stage 2 Description of CarrierAggregation” 3GPP TSG-RAN WG2 Meeting #69, San Francisco, USA, 22-26Feb. 2010]. Specifically, the PCCs (DL and UL) initially corresponds tothe cell with which the UE establishes or re-establishes the RRCconnection, and can then be changed with a handover procedure(specifically, via a security key change and RACH procedure). The UL PCCis used for transmission of L1 uplink control information. Unlike DLSCCs, the DL PCC cannot be de-activated. Re-establishment is triggeredwhen the DL PCC experiences radio link failure, not when DL SCCsexperience radio link failure. Non-access stratum information is takenfrom the cell corresponding to the DL PCC.

It is clear that a UE 10 would have only one PCC, so that if the UE 10is operating with carriers that are arranged in two or more independenttiming alignment groups, then the primary carrier timing alignmentrelates to only one of the timing groups. But simply extending the sameprocedures from LTE Release 8 for the timing advance group of LTERelease 10 for which the timer has expired is not seen to be the bestoption going forward, for reasons noted in the background section above.

Without loss of generalization, an exemplary embodiment of the inventionis shown in the flow diagram of FIG. 5. The UE which has two or moretiming advance groups begins with an independent timer for each of thosegroups that is synchronized with the eNB. Using a first one of thosetimers, at block 502 the UE 10 synchronizes its UL transmissions and itsDL receptions over allocated radio resources within a first timingadvance group. Similarly, using a second one of those timers the UE 10at block 504 synchronizes its UL transmissions and DL receptions overallocated radio resources within a second timing advance group. Thissame UE may or may not have additional timing advance groups withcorresponding timers. The UE 10 determines at some point, shown as block506, that the first timer remains synchronized while the second timer isnot synchronized with the radio network which has allocated therespective radio resources.

In accordance with an exemplary embodiment of the invention there aredifferent procedures which the UE 10 follows in response to thedetermining at block 506, depending upon whether the timing advancegroup for which synchronization is lost includes the primary componentcarrier PCC or if the PCC still has timing synchronization. Block 508 ofFIG. 5 states this more specifically for the FIG. 5 example: the UE 10follows a first procedure for the case in which there is a PCC in thesecond timing advance group, and follows a second procedure for the casein which there is no PCC in the second timing advance group. One reasonbehind this different treatment is that the primary carrier carries alluplink ACK/NACK reports in LTE Release 10, as well as CQI and SR (if SRis configured). Since the UE has only one PCC, loss of timing for thegroup carrying the PCC in LTE Release 10 means that no ACK/NACK reportsor CQI reports can be sent for the SCC groups.

Block 510 of FIG. 5 outlines some of these different proceduresaccording to a non-limiting example. If the second timing alignmenttimer which has expired is the one that is associated with the timingalignment group that does not include a primary carrier, then the UEfollows a second procedure which includes:

-   -   flush all HARQ buffers for all uplink carriers associated with        the expired second timing alignment timer;    -   clear the uplink grants, if any, associated with each of the        uplink carriers that is associated with the expired second        timing alignment timer;    -   not transmit on uplink channels associated with the expired        second timing alignment timer except for RACH channels;    -   continue to receive PDCCH that carries commands for the second        timing group associated with the expired second timing alignment        timer, but ignoring all uplink grants until the second timing        alignment timer is restarted. Downlink grants can be received        and acted upon.    -   inform the eNB that timing alignment for the group of uplink        carriers associated with the expired second time alignment timer        has failed.

If the second timing alignment timer which has expired is the one thatis associated with the timing alignment group that does include theprimary carrier, then the UE follows a first procedure which in thisexample is the same as that for a LTE Release 8 UE that loses its timingsynchronization. By example and as shown at block 510 the firstprocedure includes:

-   -   flush all HARQ buffers;    -   notify RRC to release PUCCH/SRS; and    -   clear any configured downlink assignments and uplink grants.

If the UE 10 has one or more additional timing advance groups ofcarriers for which the associated timing advance timer has not expired,such as the first timing advance group that is associated with theun-expired first timer in the FIG. 5 example, then with regard tocarriers in these groups the UE can:

-   -   continue to receive PDCCH and uplink and downlink grants for        these carriers; and    -   use uplink grants but not downlink grants, because the carrier        for sending HARQ ACK/NACK reports (the PCC) is not in time        alignment.        In an exemplary embodiment and further in response to the        determination at block 506, the UE 10 at block 512 sends a        message to the radio network indicating that the second timer        has expired. Block 514 of FIG. 5 briefly summarizes two        different formats that synchronization-failure message of block        512 may take. In all cases the message identifies that it is the        second timer, associated with the second timing advance group,        which has failed. This identification may be explicit or        implicit in how the failure message is indicted, and it may        identify the timer or the group; either one identifies the other        since each timer is associated with one and only one timer        advance group at any given time for any given eNB 12.

In one exemplary embodiment for the timing expiration message, the MAClayer of the UE 10 informs the RRC of the UE that the second timingalignment timer has expired. The RRC of the UE 10 then informs the eNB12 using an RRC message. The RRC message used may be a MeasurementReport as noted at block 514. Alternatively the message informing theeNB of timing synchronization failure is a new RRC signaling messageintroduced for the purpose of indicating timing alignment failure or amore general message designed to report more than one failure condition(for example, downlink synchronization failure for an individualdownlink carrier). At this point the eNB 12 can decide whether to bringthe timing group back into alignment by transmitting a PDCCH order onthe corresponding PDCCH channel, or do nothing and allow the secondtimer to remain un-synchronized.

If a measurement report is used to single that the second timer isexpired, in an embodiment there is a new measurement event that isintroduced, the event trigger for this new measurement event is loss ofuplink timing alignment. In one embodiment the UE 10 is configured tomonitor for this new event trigger. In this case which the measurementevent trigger is configured, the UE 10 would report the timing alignmentfailure if the UE determines that the second timer has expired. Inanother embodiment the UE10 is not configured to monitor for the newevent trigger, and so if one of the timers expires the UE would not sendthe timing expiration message.

In another exemplary embodiment for the timing expiration message, theMAC layer of the UE transmits a MAC control element CE that indicates tothe peer MAC layer of the eNB 12 that the second timer has expired. TheeNB 12 can then respond as described above for the case in which thetiming expiration message is a measurement report: transmit a PDCCHorder on the corresponding PDCCH channel, or do nothing.

Regardless of the specific form of the timing expiration message shownby example at block 514, block 516 summarized different manners in whichthat message can be sent. By non-limiting example only these areconditional and the UE 10 sends the message indicating that the secondtimer has expired by the first one of the series in block 516 thatapplies. If the UE has an uplink grant for a timing group for which ithas timing alignment (for example, for the first group in the FIG. 5example), the UE 10 can use this uplink grant to transfer the RRCmessage or the MAC CE.

Further at block 516 if instead the UE has no uplink grant on any otherUL carrier in a group whose timer has not expired, then if the UE 10 hasSR configured, it can use the SR to request an uplink grant. By examplethis request can be according to existing LTE Release 8 principles.

Still further at block 516 for the case in which the UE 10 has no uplinkgrant and no SR configured, then it can use the RACH to obtain an uplinkgrant. Again in an example this RACH process can be according toexisting LTE Release 8 principles. If the UE 10 has RACH resourcesavailable for an UL carrier that is part of the second timing group forwhich the UE 10 has lost timing alignment then the UE 10 shouldpreferably use this RACH in order that it can obtain a timing correctionfor the expired second timing advance group. If that preferred RACH isnot available the UE 10 can use a RACH on a different timing group forwhich the timer has not expired.

For the case in which the form of the message reporting expiration ofthe second timer is a MAC layer CE as at block 514, this CE can replacethe BSR that would be included under LTE Release 8 rules. This operatesto reduce the number of grants needed to complete the informationexchange. In both cases transmission of the message of block 512 isinitiated only once.

The UE 10 can also report the expiry of the second timer that isassociated with the timing advance group which includes the PCCaccording to the options shown at block 514; either an RRC/measurementreport or a MAC layer CE that is reported to the eNB 12 if the UE 10 hasan uplink grant available per block 516.

By the above exemplary embodiments, for the case in which the UE doesnot have an additional timing advance group available, then it must bethat there is no un-expired timing advance timer. This means that thePCC is in a group with an expired timer, and the end result followingthe above first procedure with no remaining synchronized timing advancegroup is that the UE 10 behaves just as a LTE Release 8 UE whose timingadvance timer has expired.

One specific technical effect of the above exemplary embodiments is thatthere is a much improved possibility to avoid triggering a radio linkfailure when a timing advance group timer expires.

FIG. 5 may be considered to be a logic flow diagram that illustrates theoperation of a method, and a result of execution of computer programinstructions, in accordance with the exemplary embodiments of thisinvention, such as for example from the perspective of the UE. Dashedlines at FIG. 5 indicate optional elements. The various blocks shown inFIG. 5 may be viewed as method steps, and/or as operations that resultfrom operation of computer program code, and/or as a plurality ofcoupled logic circuit elements constructed to carry out the associatedfunction(s).

For example, the UE and eNB, or one or more components thereof, can forman apparatus comprising at least one processor and at least one memoryincluding computer program code, in which the at least one memory andthe computer program code are configured to, with the at least oneprocessor, cause the apparatus to perform the elements shown at FIG. 5and/or recited in further detail above.

In general, the various exemplary embodiments may be implemented inhardware or special purpose circuits, software, logic or any combinationthereof. For example, some aspects may be implemented in hardware, whileother aspects may be implemented in firmware or software which may beexecuted by a controller, microprocessor or other computing device,although the invention is not limited thereto. While various aspects ofthe exemplary embodiments of this invention may be illustrated anddescribed as block diagrams, flow charts, or using some other pictorialrepresentation, it is well understood that these blocks, apparatus,systems, techniques or methods described herein may be implemented in,as non-limiting examples, hardware, software, firmware, special purposecircuits or logic, general purpose hardware or controller or othercomputing devices, or some combination thereof.

It should thus be appreciated that at least some aspects of theexemplary embodiments of the inventions may be practiced in variouscomponents such as integrated circuit chips and modules, and that theexemplary embodiments of this invention may be realized in an apparatusthat is embodied as an integrated circuit. The integrated circuit, orcircuits, may comprise circuitry (as well as possibly firmware) forembodying at least one or more of a data processor or data processors, adigital signal processor or processors, baseband circuitry and radiofrequency circuitry that are configurable so as to operate in accordancewith the exemplary embodiments of this invention.

Various modifications and adaptations to the foregoing exemplaryembodiments of this invention may become apparent to those skilled inthe relevant arts in view of the foregoing description, when read inconjunction with the accompanying drawings. However, any and allmodifications will still fall within the scope of the non-limiting andexemplary embodiments of this invention.

It should be noted that the terms “connected,” “coupled,” or any variantthereof, mean any connection or coupling, either direct or indirect,between two or more elements, and may encompass the presence of one ormore intermediate elements between two elements that are “connected” or“coupled” together. The coupling or connection between the elements canbe physical, logical, or a combination thereof. As employed herein twoelements may be considered to be “connected” or “coupled” together bythe use of one or more wires, cables and/or printed electricalconnections, as well as by the use of electromagnetic energy, such aselectromagnetic energy having wavelengths in the radio frequency region,the microwave region and the optical (both visible and invisible)region, as several non-limiting and non-exhaustive examples.

Further, the various names used for the described parameters andchannels (for example, PDCCH) are not intended to be limiting in anyrespect, as these parameters may be identified by any suitable names.

Furthermore, some of the features of the various non-limiting andexemplary embodiments of this invention may be used to advantage withoutthe corresponding use of other features. As such, the foregoingdescription should be considered as merely illustrative of theprinciples, teachings and exemplary embodiments of this invention, andnot in limitation thereof.

1. A method comprising: an apparatus synchronizing at least one oftransmissions and receptions over allocated radio resources within afirst timing advance group using a first timer; the apparatussynchronizing at least one of transmissions and receptions overallocated radio resources within a second timing advance group using asecond timer; and in response to determining that the first timerremains synchronized while the second timer is not synchronized with aradio network which has allocated the respective radio resources, theapparatus following a first procedure for the case in which there is aprimary component carrier within the second timing advance group andfollowing a different second procedure for the case in which there is noprimary component carrier within the second timing advance group.
 2. Themethod according to claim 1, in which: the first procedure comprisesflush all hybrid automatic repeat request buffers; and the secondprocedure comprises flush all hybrid automatic repeat request buffersfor all uplink carriers associated with the expired second timer.
 3. Themethod according to claim 2, in which: the first procedure furthercomprises clearing any configured downlink grants and uplink grants; andthe second procedure comprises: clearing any uplink grants associatedwith any uplink carrier in the second timing advance group; and actingupon all downlink grants associated with any downlink carrier in thesecond timing advance group.
 4. The method according to claim 3, inwhich: the first procedure comprises notifying radio resource control torelease a physical uplink control channel and sounding reference signalbits; and the second procedure does not comprise notifying radioresource control to release a physical uplink control channel andsounding reference signal bits.
 5. The method according to any one ofclaim 1, further comprising: the apparatus sending a message to theradio network indicating that the second timer has expired.
 6. Themethod according to claim 5, in which the message indicating that thesecond timer has expired comprises a measurement report which istriggered to be sent by the expiration of the second timer.
 7. Themethod according to claim 5, in which the message indicating that thesecond timer has expired comprises a control element indicating that thesecond timer has expired.
 8. The method according to claim 5, in whichthe message indicating that the second timer has expired is sent on agranted uplink radio resource within a carrier of the first timingadvance group.
 9. (canceled)
 10. (canceled)
 11. (canceled)
 12. A memorystoring a program of computer readable instructions that when executedby a processor result in actions comprising: synchronizing at least oneof transmissions and receptions over allocated radio resources within afirst timing advance group using a first timer; synchronizing at leastone of transmissions and receptions over allocated radio resourceswithin a second timing advance group using a second timer; and inresponse to determining that the first timer remains synchronized whilethe second timer is not synchronized with a radio network which hasallocated the respective radio resources, following a first procedurefor the case in which there is a primary component carrier within thesecond timing advance group and following a different second procedurefor the case in which there is no primary component carrier within thesecond timing advance group.
 13. (canceled)
 14. An apparatus comprising:at least one processor; at least one memory including computer programcode; the at least one memory and the computer program code configuredto, with the at least one processor, cause the apparatus at least to:synchronize at least one of transmissions and receptions over allocatedradio resources within a first timing advance group using a first timer;synchronize at least one of transmissions and receptions over allocatedradio resources within a second timing advance group using a secondtimer; and in response to determining that the first timer remainssynchronized while the second timer is not synchronized with a radionetwork which has allocated the respective radio resources, follow afirst procedure for the case in which there is a primary componentcarrier within the second timing advance group and follow a differentsecond procedure for the case in which there is no primary componentcarrier within the second timing advance group.
 15. The apparatusaccording to claim 14, in which: the first procedure comprises flush allhybrid automatic repeat request buffers; and the second procedurecomprises flush all hybrid automatic repeat request buffers for alluplink carriers associated with the expired second timer.
 16. Theapparatus according to claim 14, in which: the first procedure furthercomprises clearing any configured downlink grants and uplink grants; andthe second procedure comprises: clearing any uplink grants associatedwith any uplink carrier in the second timing advance group; and actingupon all downlink grants associated with any downlink carrier in thesecond timing advance group.
 17. The apparatus according to claim 14, inwhich: the first procedure comprises notifying radio resource control torelease a physical uplink control channel and sounding reference signalbits; and the second procedure does not comprise notifying radioresource control to release a physical uplink control channel andsounding reference signal bits.
 18. The apparatus according to any oneof claim 14, in which the memory and the computer program code areconfigured with the at least one processor to further cause theapparatus, in response to the determining, to send a message to theradio network indicating that the second timer has expired.
 19. Theapparatus according to claim 18, in which the message indicating thatthe second timer has expired comprises a measurement report which istriggered to be sent by the expiration of the second timer.
 20. Theapparatus according to claim 18, in which the message indicating thatthe second timer has expired comprises a control element indicating thatthe second timer has expired.
 21. The apparatus according to claim 18,in which the message indicating that the second timer has expired issent on a granted uplink radio resource within a carrier of the firsttiming advance group.
 22. The apparatus according to claim 21, in whichthe memory and the computer program code are configured with the atleast one processor to further cause the apparatus to re-synchronize thesecond timer after the second timer expires using a timing correctionobtained on a carrier of the first timing advance group.
 23. Theapparatus according to claim 18, in which the message indicating thatthe second timer has expired is sent on an uplink radio resource that isgranted in response to sending a request for the uplink radio resourceusing a configured scheduling request, for the case which, at the timethe second timer expires, there is no granted uplink radio resourcewithin a carrier of the first timing advance group but there is ascheduling request configured.
 24. The apparatus according to claim 18,in which the message indicating that the second timer has expired issent on an uplink radio resource that is granted in response to sendinga random access request, for the case in which, at the time the secondtimer expires, there is no granted uplink radio resource within acarrier of the first timing advance group and there is no schedulingrequest configured.